Transplantable hormone producing tumors, particularly an insulin producing hamster pancreatic beta cell tumor, will be utilized to study the regulation of insulin secretion. The role of calcium and cyclic AMP on the regulation of secretion will be explored by studying the effect of various secretagogues on calcium uptake, adenylate cyclase. To explore the mechanisms of cyclic AMP action, antibodies of cyclic AMP dependent protein kinases will be utilized to study the heterogeneity, production, degradaton and state of association of these kinases.